Adaptive Spatial Modulation for Visible Light Communications With an Arbitrary Number of Transmitters

Abstract

As a power and bandwidth efficient modulation scheme, the optical spatial modulation (SM) technique has recently drawn increased attention in the field of visible light communications (VLC). To guarantee the number of bits mapped by the transmitter's index at each timeslot is an integer, the number of transmitters (i.e., light-emitting diodes) in the SM based VLC system is often set be a power of two. To break the limitation on the required number of transmitters and provide more design flexibility, this paper investigates the SM based VLC with an arbitrary number of transmitters. Initially, a channel adaptive bit mapping (CABM) scheme is proposed, which includes three steps: bit mapping in space domain, bit mapping in signal domain, and the channel adaptive mapping. The proposed CABM scheme allows operation with an arbitrary number of transmitters, and is verified to be an efficient scheme through numerical results. Based on the CABM scheme, the information-theoretical aspects of the SM based VLC are analyzed. The theoretical expression of the mutual information is first analyzed. However, it is very hard to evaluate system performance. To obtain more insights, a lower bound of the mutual information is derived, which is in closedform. Both theoretical analysis and numerical results show that the gap between the mutual information and its lower bound is small. Finally, to further improve the system performance, the precoding scheme is proposed for the SM based VLC. Numerical results show that the system performance improves dramatically when using the proposed precoding scheme.

On the Secrecy Rate of Spatial Modulation-Based Indoor Visible Light Communications

“…In Fig. 8, for small h B /h E , the performance gaps between (20) and (22) are small and they can be ignored. Moreover, the secrecy rate bounds do not change with A for small h B /h E , which is similar to the conclusion in Fig.…”

“…6(b), the performance gaps between the lower bound (20) and the upper bound (22) is provided in Table IV. In this case, the asymptotic performance gap at high SNR is about 0.2676 nat/transmission, which is the same as the result in Remark 3. upper bounds of secrecy rate (22) always increase with the increase of ξ. Moreover, the larger the peak optical intensity A is, the slower the increasing trend of the upper bound (22) becomes.…”

Capacity analysis of cooperative amplify and forward multiple‐input multiple‐output systems

“…In general, it has been shown in the literature that SMTs can be implemented with a maximum of single RF chain at the transmitter, regardless how many transmit antennas exist, 11 along with high spectral efficiency, high energy efficiency, and low implementation costs. As such, they attracted substantial research interests and have been considered with variant application, as optical communication, 18 Internet of Things (IoT), 19 underwater communications, 20 unmanned aircraft, 21,22 and molecular communications 23 along with many other research areas [24, and references therein].…”

Precoded Optical Spatial Modulation for Indoor Visible Light Communications

“…Moreover, in order to improve the secrecy performance, the authors of [35] derived bounds for the secrecy rate of indoor SM-VLC systems, and proposed channel adaptive selection and greedy selection schemes to select the active transmitter. A constellation selection algorithm was proposed for OSM to minimize the average transmit power in [36], while a channel-adaptive bit mapping rule was proposed for OSM to provide more design flexibility in [37]. More recently, based on the results in [37], the bit-to-symbol mapping problem in OSM was further investigated in [38] and [39].…”

“…A constellation selection algorithm was proposed for OSM to minimize the average transmit power in [36], while a channel-adaptive bit mapping rule was proposed for OSM to provide more design flexibility in [37]. More recently, based on the results in [37], the bit-to-symbol mapping problem in OSM was further investigated in [38] and [39].…”